A Holter monitor is a machine that continuously records the heart's rhythms. The monitor is worn for 24 to 48 hours during normal activity.
Electrodes (small conducting patches) are stuck onto your chest. These are attached by wires to a small recording monitor. You carry the Holter monitor in a pocket or pouch worn around your neck or waist. The monitor runs on batteries.
While you wear the monitor, it records your heart's electrical activity.
It is very important that you accurately record your symptoms and activities so the provider can match them with your Holter monitor findings.
Electrodes must be firmly attached to the chest so the machine gets an accurate recording of the heart's activity.
While wearing the device, avoid:
Continue your normal activities while wearing the monitor. You may be asked to exercise while being monitored if your symptoms have occurred in the past while you were exercising.
You DO NOT need to prepare for the test.
Your provider will start the monitor. You'll be told how to replace the electrodes if they fall off or get loose.
Tell your provider if you are allergic to any tape or other adhesives. Make sure you shower or bathe before you start the test. You will not be able to do so while you are wearing a Holter monitor.
This is a painless test. However, some people may need to have their chest shaved so the electrodes can stick.
You must keep the monitor close to your body. This may make it hard for you to sleep.
Occasionally there may be an uncomfortable skin reaction to the sticky electrodes. You should call the provider's office where it was placed to tell them about it.
Holter monitoring is used to determine how the heart responds to normal activity. The monitor may also be used:
Heart rhythms which may be recorded include:
Normal variations in heart rate occur with activities. A normal result is no significant changes in heart rhythms or pattern.
Abnormal results may include various arrhythmias such as those listed above. Some changes may mean that the heart is not getting enough oxygen.
Other than the uncommon skin reaction, there are no risks associated with the test. However, you should be sure not to let the monitor get wet.
Reviewed By: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.